1. Technical Field
The present invention relates to an epoxy resin composition for encapsulating a semiconductor and a semiconductor device therewith.
2. Related Art
Electronic components such as diodes, transistors and integrated circuits have been typically encapsulated with an epoxy resin composition. Particularly, in integrated circuits, there have been used epoxy resin compositions exhibiting excellent heat resistance and moisture resistance containing an epoxy resin, a phenol resin curing agent and inorganic fillers such as fused silica and crystalline silica. However, recent market trend to size reduction, weight saving and higher performance in electronic devices has led to more integrated semiconductors and accelerated surface mounting of a semiconductor device, while requirements to be met by an epoxy resin composition used for encapsulating a semiconductor element has been increasingly diversified and stricter. In particular, now that surface mounting of a semiconductor device is common, a moistened semiconductor device is exposed to a high temperature during a solder reflow process. Furthermore, as part of eliminating environment burden materials, a solder free from lead has been increasingly used as an alternative material, but a lead-free solder has a higher melting point than a conventional solder. Therefore, it needs a reflow temperature during surface mounting higher by about 20° C. than a conventional case, specifically 260° C. Thus, a semiconductor device is exposed to a further higher temperature, causing de-lamination of a cured epoxy resin composition in its interface with a semiconductor element or lead frame. It tends to defects significantly deteriorating reliability in a semiconductor device such as cracks.
Furthermore, also from environmental considerations, there is a move to limit the use of a halogen-containing flame retardant such as bromine-containing organic compounds and an antimony compound such as diantimony trioxide and diantimony tetroxide which have been used as a flame retardant for a semiconductor encapsulating material, and there has been needed alternative flame resisting means. As alternative flame resisting means for a semiconductor encapsulating material, there has been proposed the use of metal hydroxides such as aluminum hydroxide and magnesium hydroxide. They must be, however, used in a large amount for effectively working as a flame retardant, and when being used in an enough amount to be a flame retardant, it may deteriorate flowability and curability of an epoxy resin composition during molding, mechanical strength of a cured material and thus solder-reflow resistance in a temperature range for mounting the above lead-free solder.
To solve these problems, there have been proposed using a low water-absorbing, flexible and flame-resistant resin for meeting the requirements for both solder reflow resistance and flame resistance (See, for example, Japanese Patent Application Laid Open Nos. 1989-275618, 1993-097965 and 1993-097967). However, there have been needed further higher solder-reflow resistance while recently a semiconductor has been further thinner and interconnections have been further finer, so that improvement in flowability during encapsulating and molding. It has been, therefore, difficult to meet all of these requirements.
Given such circumstances, there has been needed for developing a resin composition for encapsulating a semiconductor exhibiting higher flame resistance, good flowability and adequately higher solder-reflow resistance to allow for the use of a lead-free solder without a flame retardant.
Thus, this invention provides an epoxy resin composition for encapsulating a semiconductor exhibiting higher flame resistance, good flowability and adequately higher solder-reflow resistance to allow for the use of a lead-free solder without a flame retardant, as well as a highly reliable semiconductor device in which a semiconductor element is encapsulated with a cured product from the composition.